Digital data is recorded on a slant track of a magnetic tape by a rotary head, in which the sampling frequency of the digital data can be changed in accordance with the nature of the digital data. The recording apparatus comprises a memory for writing the digital data in response to an input clock signal which is synchronized with the sampling frequency and reading the digital data therefrom in response to a system clock signal; and a circuit for converting the digital data read out from the memory into a data block having such a capacity that the data block can be recorded during one scan of the rotary head. Even when the data rate of the input digital signal is unclear, if the data rate lies within a range where the buffer memory does not overflow, the apparatus can continuously record the input digital signal. Thus, the apparatus can easily interface with an external computer.